It is a requirement in most countries according to the national building codes thereof and the fire prevention organizations therein, to provide exit signs near main exits from the lobby of, for example, offices. Most exit signs found within the prior art are powered by either incandescent or fluorescent bulbs contained within a housing having the letters "EXIT" embossed or otherwise fashioned in a plastic planar member wherein the letters are illuminated by the bulbs contained within the exit sign and the background for the letters is normally covered and opaque. Further, there are normally slits in the bottom portion of the exit sign to allow for some down lighting when the main office lighting is shut off either by emergency or necessity.
It is quite customary to power the exit signs by standard 110 Volt A/C current during normal operations and to provide either battery or generator back up for lighting the exit sign during emergencies. In one example of an exit sign, three sockets are provided within the sign which provides for the outer two bulbs being lit during normal operation and the inner bulb being lit during emergency operation.
The afore-mentioned structure is typical of an exit sign found in the prior art wherein the illumination level of the exit sign decreases during the emergency requirement of said exit sign contrary to the desirable attributes of an effective exit sign.
A report prepared by the National Research Council of Canada published in June, 1985, Article No. 24627, entitled "Photometric And Psychophysical Measurements Of Exit Signs Through Smoke", discusses in detail the variables which contribute to the effectiveness of exit signs. One of the main recommendations of the report was that the illumination or brightness of the sign was one of the most important factors in determining the visibility of said exit sign in smoke-filled rooms. Further, it was found that any down lighting embodied as part of prior art exit signs scattered in the smoke and created a degrading effect during the emergency for the exit sign.
Another type of sign found within the prior art is the self-illuminating sign used as an exit sign providing Beta radiation induced by chemi-luminescence of tritium gas. However, such exit signs have been found to be insufficient during an emergency and are questionable as to their visibility as itemized in the afore-mentioned report of the National Research Council.
Beyond the effectiveness of the sign, there is the concern for radiation and such signs must be properly monitored to ensure that there is no leakage from the source and hence creating a real safety hazard instead of being a piece of operating safety equipment.
U.S. Pat. No. 3,026,436, by Hughes, is such a typical device. Although the radioactive material is a phosphorescent material, the principles are very closely resembling products available today.
If a power outage occurs, it is of course desirable for the emergency exit sign to stay lit to provide guidance to the occupants of the building for a safe exit therefrom. However, it is a common feature of incandescent bulbs that those bulbs which have or are approaching their life expectancy may fail during such a power outage, especially if the power outage is caused by a surge thus rendering any exit sign useless. Those bulbs which are weakened because of the surge during the power failure may further fail when the current is turned back on again. Incandescent bulbs also have a problem in that they dissipate a great deal of the energy which they draw as heat. Such heat accumulating in the housing of the exit sign and possible causing an overheating situation destroying members within the exit sign or worse causing a fire.
Fluorescent bulbs on the other hand have other disadvantages well known within the prior art. For example, a ballast resistor must be provided in order to effectively light a fluorescent tube. Ballast resistors are not effective in -45.degree. C. temperature operation as may be the case if the sign were placed within an unheated area or be used externally. It has been found however that LED's (Light Emitting Diodes) do not have such a severe temperature limitation as the operating considerations for fluorescent tubes.
Another consideration from the practical standpoint of exit signs is the maintenance program which must be put in place in order to maintain them, especially when considering a large office structure or complex. If we would consider one exit sign only having three bulbs therein with a lifetime expectancy of approximately four months each, it can be readily seen that a total of nine bulbs will be used in the exit sign for an annual period. These bulbs must be changed by a qualified technician and in some organizations because of union contract requirements an electrician must obtain an extension ladder and replace the burnt out bulbs. Also one must consider for the total cost of the maintenance of such an exercise, the power consumption of the sign, assuming three 15 Watt incandescent bulbs, the cost will vary depending upon the hydro rates within the area of installation. However it is well known that LED's have a considerable longer life than light bulbs or even fluorescent tubes expected to be of the order of thirty years and have considerably less power consumption than the afore-mentioned structures. Further the exit sign components as described herein are effectively shock resistant and rugged in construction withstanding vibration and blows beyond those of incandescent or fluorescent lighting systems.
It is desirable to only light the letters within the exit sign structure and not light all of the remaining area of the sign.
Although discussing the prior art to this invention in relation to exit signs, one may generalize and say that signs in general giving information or direction to the public such as "NO SMOKING", "NO EXIT", "ENTER", or "EXIT/SORTIE", in any language whatsoever "OPEN", "CLOSED", or house numbers or house names would be applicable when considering the maintenance thereof in relation to the applicant's invention. It is therefore not applicant's intention to limit the invention to only exit signs but exit signs are the preferred embodiment of the invention.
U.S. Pat. No. 2,354,367 discloses a display sign as best seen in FIGS. 1 and 4 and described at column 2, line 73 through column 4, line 24, wherein the side surface of the letters is cut in order to provide the diffusion of the light passing through the rods and said rods comprising a bar of methyl-methacrylate. However the light source is not embedded in the rod nor is the light source a light-emitting diode having great reliability in contrast to an incandescent bulb as illustrated in FIG. 1.
U.S. Pat. No. 2,448,244, by Arnold, discloses an illuminated display device having inserted at the end thereof similar to a flashlight a light 100 as best illustrated in FIG. 3 being adjacent the end of a light pipe described at column 2, line 30, made of water white methyl methacrylate resin especially having a relatively high index of refraction and a low critical angle and low absorption of visible light. However such a light pipe does not have an LED embedded in the end thereof to allow light to pass through the sides thereof but the light shines through similar to an optical fibre to the end 103 in FIG. 3.
U.S. Pat. No. 3,578,973 discloses a self-luminous light source having the source embedded in one end thereof a fiber optic type media wherein the light travels to the end of the optical fiber as best illustrated in FIGS. 2 and 3A. Further, since the source is a radioactive source, it is preferred that a bend in the light path be provided to contain the radioactivity in the source. In emergency situations the operation thereof is questionable as described in relation to U.S. Pat. No. 3,026,436.
Another example of a self-illuminating light-emitting unit is found in U.S. Pat. No. 3,409,770 wherein the sources are located within a groove within a plastic body 13 made from transparent polymethylmethacrylate described at column 3, line 65. A transparent elastomeric potting material 17 is then filled in the groove 14 around the tube 10 and the elastomeric cushions 16. A low-temperature curing transparent silicone gel is especially suitable for the potting material. The entire exterior surface body 13 is coated with a light-reflective white paint 20, the practical effect of which is to greatly enhance the uniformity and efficiency of the distribution of light within the unit. The function of the white paint 20 is to provide an opaque coating about the entire body of the unit which reflects as much of the light as possible back into the body and eventually permits it to be transmitted undiminished through the window area. The light source is a particulate phosphorous layer to adhere to and exposed on the phosphoric acid film and a radioactive beta-ray emitting gas within the element. The light is transmitted at 20 as shown in FIG. 2 in a linear relationship with the source within the cavity.
U.S. Pat. No. 3,972,139, by Slomkowski, discloses a device for displaying numbers using bulbs at 60 and a facing 64 wherein the light reflects along a reflective surface 34 as best illustrated in FIG. 3.
U.S. Pat. No. 2,507,909 describes an advertising display using light pipes wherein the light is transferred to the end of the pipe but not on the side thereof.
French Publication No. 2,431,659 as best illustrated in relation to FIGS. 7 and 13 describes a device which can be used for display signs wherein light transfers to the end of the optical fiber.
Nowhere within the prior art is there found an exit sign which increases in illumination during emergency procedures nor which flashes. Further, nowhere within the prior art is there found display signs constructed from light pipes having light-emitting diodes embedded in the ends thereof which illuminate only the letters of the display sign or the pattern of the display and which substantially reduces the maintenance and cost of operation of such exit signs. It is also not disclosed within the prior art to provide an exit sign which is durable and rugged which may withstand the beating which exit signs take especially those installed within institutions such as schools and public housing projects where vandalism is a main concern for superintendents of the buildings.
It is therefore an object of this invention to provide an exit sign and components therefor which overcome all of the afore-mentioned problems in the prior art reducing the maintenance and operating costs of said signs and increasing the life expectancy thereof.
It is further object of this invention to provide lighting elements which are used within display signs which drastically reduce the safety hazards and energy waste of the heat generated within conventional display signs.
It is a further object of this invention to provide an exit sign which may be used in conjunction with security or fire systems installed within buildings in order to carry out special functions and features embodied with the sign.
Further and other objects of the invention will become apparent to a man skilled in the art when considering the following summary of the invention and the more detailed description of the preferred embodiments illustrated herein.